Water hardening mixtures



I United States Patent Ofiice 2,899,326

Patented Aug. 11, 1959 In order to determine the efiect of calcined alumina on a simple mixture of Portland cement and water, I prepared a control mixture of cement and water in the 2,899,326 proportions of 1500 grams of cement to 575 grams of WATER HARDENING MIXTURES Donald H. Butler, Pittsburgh, Pa.

No Drawing. Application August 24, 1956 Serial No. 605,951

4 Claims. (Cl. 106-97) water and measured the flow characteristics. I then prepared a mixture of cement and calcined alumina containing alumina in the proportion of 6% by weight of the cement. To the mixture of cement and alumina, I added water in varying amounts until I secured the same flow characteristics as the control sample. The flow characteristics were measured in accordance with the A.S.T.M. C-230-55T flow test method. The mixture was allowed to harden for seven days and then tested for strength. I obtained the following results:

This invention relates to water hardening mixtures, more particularly to water hardening mixtures including TABLE I as an ingredient a calcium-containing cement such as Portland cement, plaster ((CaSO H- O), or aluminous Flow Shengthm cement (CaO.Al O +2CaO.SiO My invention 9011- Mlx A1103 percent lbs./sq.ln. sists in a mixture of a water hardening calcium-contain- Hays ing cement and calcined alumina in certain proportions 1 500 t 575 t N 67 1 650 by weightto the cement whereby some of the physical gt'wa 1 properties of both the wet and hardened cement are ma- L500 cement 563g iniaiii? 67 M80 terially improved, particularly workability or placeability, strength, and heat conductivity.

This application is a continuation in part of my copending application, Serial No. 313,990, filed October 9, 1952, now abandoned.

I have found that, if calcined alumina is added to water hardening calcium-containing cements in proportions hereinafter stated, the workability, placeability, or ability of the cement to flow after a given amount of water is added is materially improved. Conversely, if calcined alumina is added to the cement, the same workability, placeability, or ability to flow can be obtained with less water than would otherwise be required. Reduction in the amount of water required to place and harden a calcium-containing cement, for example, Portland cement, produces important results. Reduction in the amount of water increases the strength of the hardened cement and its heat conductivity. I am not certain as to why the addition of calcined alumina materially improves This test shows that, by addition of calcined alumina, I could obtain the same flow or placeability with less water. The test also shows that the strength of the hardened mixture was greatly increased.

In another series of tests using mixtures of Portland cement and crystalline alumina in the form of calcined alumina, I used a control mixture comprising 1500 grams of Portland cement and 575 grams of water and, to prepare the test samples, I added to this mixture calcined alumina in varying amounts. I also decreased the amount of water used in each test sample to prevent the samples to which alumina had been added from flowing so freely as to be unmeasurable. The samples were tested for flow and then allowed to harden for seven days and tested for strength. The results of the tests are set out in the following table:

certain of the physical properties of calcium-containing TABLE 1 cements, but I believe that its effect is to produce a better distribution of the water through the cement. In any A1203, Strengthm event, numerous tests and experiments which I have con- Mlxpercent of Flow, lbs./sq. in. ducted establish that the physical properties are, in fact, 3 5%,? percent days improved.

I have found that calcined alumina should be added 1,5001% cement 575 None 67 1,650 to cement in the proportion of from 2 to 15% by weight 1,500 gr. cement, 548 gr. water g of the cement. I have also found that substantially all 5 116 3:599 of the particle size of the calcined alumina particles g 133 2, 1 0 3 should be at least as large as the cement particles to 8 n2 6:370 which the alumina is added. If the particle size of the 9 96 6.080

alumina added is smaller than the particle size of the cement to which the alumina is added, then the alumina particles will coat the cement particles and prevent the proper combination of water and cement particles.

I have found that the commercial product known as calcined alumina has the proper characteristics for carrying out my invention. Calcined alumina is aluminum oxide which has been heated in a kiln to a temperature between 2000 F. and 2300 F. It has a crystalline structure and has a specific gravity varying from 3.6 to 3.9. A typical screen analysis of calcined alumina is:

fragments with a cementing material to form concrete,

Percent plaster, or the like. Aggregates conventionally used On 100 mesh 2-6 with Portland cement are sand, gravel, pearlite or slag On 200 mesh 5070 or a combination of these materials, and the aggregate On 325 mesh 88-96 generally used with plaster is sand or pearlite. Through 325 4-12 Using a mixture of Portland cement, sand, and water,

By aggregates, I mean any hard, inert natural or manufactured material mixed in graduated 3 4 I kept the water constant but added calcined alumina in TEST o, 2 varying amounts and obtained the results set out in the following table: Cement nm 517 517 TABLE 111 .9% it: 113% H 5 Men 2315-- as 22 A120, lbs None 35 A1101, Strength in slump inrhns I 4 2. 5 percent Flow, J q- 13 st t 1bs./sq.in 2,500 4,685 Mix of cement percent by weight After After w w 'rns'r N0. 3

"gfig fiifffj ff fffi fi- None 40 1,616 2. 5,21 "l5? 1,233 11,233 D 2 56 1,568 2,051 Shot Gram lbs 1,900 1,900 3 44 1, 2 Water gals 37.5 27 4 62% 1,578 2,406 A110, lh None 35 5 62 i, 51% Slumpinches 4 6 49; g 3 1:720 2:323 28Day Strength .J -l q- 2,800 I s 58 1, 682 x 22 i 2:628 TEST N0. 4 12 g 34 'ii 1m 500 590 ii 50 11731 2:615 "1115,- 1,300 1,300 15 40 1,824 2, 816 %n Gravel lbs 1, 900 l, 900 ater nals 38 33 AlzO- ll: Nong 32 This table shows that the additiO 0f calcined alumina g fi gi'figg lbs,/sq. in 2,700 3,790 over a certain range and with the same amount of water increased the strcngth and percentage fl i table It will be noted that in each test the strength of the shows that the strength increased as calcined alumrna was concrete was very materially increased although the added up to 15% by weight of cement. When calcined gravel portions of the aggregates in the mhmmas dug alumina was added in this amount, however, the flow or feted in size and type It will also he noted that the Placeabilily of the mixture was or It had the Same amount of water required was materially decreased and value as the control mixture. The flow value, however, also that the was decreased. In spite of the started to decrease when the calcined alumina amounted fact h the water was decreased and the Slump fi u to 3 or 9% by weight of cement: There is thus. a rage decreased when calcined alumina was added to the mixof proportions of calcined alumina to cement n which tures (except in one instance in which the Slump fi re one may select any f' depenfimg i was maintained), which normally would indicate a dethe results desired Thus 1f maxlmum flow 1s f crease in workability, I found that, in each mixture Proportions in the neighborhood of 5 to 7% by welght using alumina, the workability of the mixture was not of calcined alumina to cement should be affected. Moreover, the increased strengths obtained ever greater strength is required and Is not through the use of alumina were considerably higher especially desired characteristic, then the calcined alumithan would have been expected if the slump f the recom n c be added p to Increased flow F of 40 mended mixes without alumina were made the same as Co be Obtained by adding water as 15 those which were obtained by the addition of alumina known, this will affect adversely the strength of the conin the test mixes. This is shown f Test No. 4 in C e which the slump figures were the same but in which I have also added calcined alumina to concrete, 1.e., the Strength f the mix to which alumina had b Portland cement, Sand gravel, and water: and I have added was considerably greater than the strength of the found that the same improved results are obtained when recommended mix without ahhhina alumina is added to these mixtures as are obtained when I ha,e also tested the fi t f adding alumina to alumina is added to Portland cemem alone ventional wall plaster by plastering three houses with a tures of sand and Portland cement. The results of tests conventional wall plaster i (gypsum, 00 pounds, and on the addition of calcined alumina to concrete are set pearhte, 2 cubic feet) To this conventional mix and out in th table belOW- In making tests I used before adding water, I added alumina in the proportion mixtures prescribed by Committee 613 of the American f 5% by weight f the gypsmm I found h h d i- Concrete Institute in a report entitled Recommended fioh f the alumina reduced h water i h ld PraC C for Selecting Proportions Concrete? T0 be required for a mix without alumina by approximately fl'wse Prescribed mixtures, I added calcined alumina as 25 to 30%. The result was that the houses in which set out in the table and tested only the mixtures conthe plaster was installed were ready for fi i hi 30% m g e alumina- In the table bdowilhe figures under sooner than would have been the case if conventional the columns headed Rec. are the quantities of raw plasters h b d, materials sPeclfied y the Committee of the Amen'can Calcium aluminate is used as a refractory cement, as Concrete Institute to obtain the slump and strength chara mortar f holding r f a tory hn'cks together i a acteristics indicated. The figures under the columns f a f r the l i of h l or h repairing of headed Tesf are the COIIIPOSitiOHS which I made and holes formed in a refractory lining of a furnace during tested and the results which I obtained from my tests. use and when mixed with an aggregate as a castable for special heat-resistant shapes. I prepared a mixture of TABLE IV calcium alurninate and calcined alumina in the propor- TEST No. 1 tion of 6% by weight of alumina to the calcium aluminate and found that, when the alumina was mixed with Rec. Test the calcium aluminate, it was possible to reduce the amount of water required to obtain the desired flow genaent. 39 3 8 characteristics by 25%. From this reduction in water, jl Rock lbs 1:350 1:850 it can be expected that the mlxture of calcium aluminate ater gals 3 and alumina will produce less shrinkage and therefore 3 il: less cracking than a cement of calcium aluminate alone. zsna 'stmn th ..1bs./sq.in. 3,200 5,000 Likewise, the mixture of calcium aluminate and alumina will have a higher density and therefore a greater strength than a mortar or castable made of calcium aluminate alone.

While I do not understand the exact nature of the action of the calcined alumina in cements containing calcium, it is clear that such additions in the proportions described have important results. The alumina increases the strength of the mixture containing the calcium cement if the proportion of water to cement is kept the same. The strength is even further increased if the water is decreased. If the proportion of water remains the same and if alumina is added, the flow or placeability of the cement is increased.

It is generally agreed that, where in any given mix the quantities of cement and aggregate remain the same, any increased strength obtained is due to increased density and that increased density in turn is due to a decrease in the amount of water used in the mix. Under such circumstances, the increased density will also produce increased heat conductivity in the concrete formed after the mix has set. In tests on experimental floor slabs, I have found that the heat conductivity of concrete is increased by the addition of calcined alumina. I attribute this to the fact that the addition of calcined alumina to calcium-containing cements decreases the quantity of water required for a concrete mix having the desired floor characteristics.

While I have described certain presently preferred embodiments of my invention, it is to be understood in the art that these ingredients can be used alone or with any of the aggregates described above.

I claim:

1. A water hardening mixture consisting essentially of a water hardening, calcium containing cement and calcined alumina, the alumina being in the proportions of 2 to 15 percent by weight of the cement.

2. A water hardening mixture consisting essentially of Portland cement and calcined alumina, the alumina being in the proportions of 2 to 15 percent by weight of the cement.

3. A water hardening mixture consisting essentially of a calcium containing, heat resistant cement and calcined alumina, the alumina being in the proportions of 2 to 15 percent by weight of the cement.

4. A water hardening mixture consisting essentially of a calcium containing plaster and calcined alumina, the alumina being in the proportions of 2 to 15 percent by weight of the cement.

References Cited in the file of this patent UNITED STATES PATENTS 848,439 Buchner Mar. 26, 1907 1,541,220 Hutchins June 9, 1925 1,553,105 Power Sept. 8, 1925 1,633,790 Lindstrom June 28, 1927 1,744,547 Hasselback Ian. 21, 1930 OTHER REFERENCES Handbook of Chemistry, Lange, 8th ed. 1952, page 196. 

1. A WATER HARDENING MIXTURE CONISSTING ESSENTIALLY OF A WATER HARDENING, CALCIUM CONTAINING CEMEMT AND CALCINED ALUMINA, THE ALUMINA BEING IN THE PROPORTIONS OF 2 TO 15 PERCENT BY WEIGHT OF THE CEMENT. 